Evaluation of ICESat-2 Atmospheric Products Using the CALIOP and CATS Spaced-Based Lidars

[13-Dec-2023]
Abstract:  The Ice, Cloud, and land Elevation Satellite (ICESat-2) was launched in September 2018 and carries one instrument called the Advanced Topographic Lidar Altimeter System (ATLAS) that utilizes a high repetition rate (10 KHz), low per pulse energy (100 µJ) laser and photon counting detectors. While ICESat-2 is designed as a high-resolution altimeter, it also contains a single 532 nm atmospheric channel to capture backscatter profiles from 14 km to the surface. Atmospheric data products have been generated from ATLAS data that include calibrated attenuated backscatter profiles, cloud and aerosol layer heights, column optical depth and many others (ATL09). Since funding for validation activities was very limited for the ATL09 products, coincident (in space and time) observations with the Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) are used to evaluate and compare with the ATL09 products. In analyzing many of the coincident CALIOP-ICESat-2 observations from intersecting orbits, we find ICESat-2 atmospheric products compare favorably to their CALIOP analogs. Calibrated attenuated backscatter profiles are highly correlated and cloud and aerosol layer detection and altitudes are very similar between CALIOP and ICESat-2, especially at night. Seasonally and spatially, ICESat-2 cloud detection compares well to the global patterns observed by the Cloud-Aerosol Transport System (CATS) and CALIOP lidars. Considering the gap in available space-based lidar data for atmospheric applications before the upcoming Atmosphere Observing System (AOS) mission, further refinement and development of ICESat-2 atmospheric products is warranted.